The lineage view, with redacted entries for nodes the caller's grant does not cover, plus the gateway attestation.
Sends GET /v1/data/:dataPointId/lineage[/:version] with a Web3Signed
Authorization header: aud = the gateway origin, uri =
gatewayLineagePath (lowercase id, version segment included),
empty-body bodyHash, and the lowercased grantId claim when given. The
gateway answers a uniform 404 for an unknown data point and for a signer
it will not serve, so the two cannot be told apart from outside.
Read a data point's lineage from the gateway.